1. Field of the Invention
The present invention relates to a strip storage unit for a continuous operation of rolling mill trains, particularly a loop-forming strip storage unit for sheet metal strips in strip treatment plants. The strip storage unit includes a loop carriage having at least one deflection roller for a strip loop. The loop carriage is movable on guides for changing the length of the loop. Support carriages which are also movable on guides and are provided with at least one support roller for the strip are connected to the loop carriage through traction members, such as, ropes, chains or the like. The strip storage unit further includes at least one feed roller and a run-out roller for the strip.
2. Description of the Related Art
Strip storage units for rolled strip are necessary for the continuous operation of rolling mill stands in rolling mill trains. Strip storage units are also required when individual coils which must be connected to each other before being introduced into the rolling mill train, are to be fed to the rolling mill train or rolling mill stand and are to be rolled in the stand. In order to avoid a slowdown of the rolling speed or even an interruption of the operation of the rolling mill train or the rolling mill stands, a loop-type storage unit and a loop forming unit of some type must be provided whose capacity is such that the strip can still be continuously fed to the rolling mill stand or rolling mill train if the individual coils must be prepared for welding together. Similar considerations are applicable to other plants which process metal strip, for example, pickling plants or annealing furnaces, which must be operated continuously and in which the different speeds of the strips being introduced must be compensated. Depending on the available space, looping towers, looping pits or horizontally extending loopers are used.
Horizontally extending loopers or horizontally arranged strip storage units are known in the art, particularly from German Offenlegungsschrift 1,953,169, Austrian patent 299,103 and European patent application 0,110,864.
The horizontally extending looper according to according to German Offenlegungsschrift 1,953,169 for strip processing plants with loop carriage and support rollers is characterized in that the support rollers are supported in several so-called trailers which are movable in horizontal direction. The ropes which connect the trailers and the loop carriage are wound onto drums and are kept in constant tension by the drives of the drums. When the loop carriage is moved in order to shorten the length of the supply loop, the loop carriage pushes the trailers ahead. Accordingly, the restoring force exerted by the rope drum drive merely has the purpose to keep the connecting ropes in a tensioned state, so that each following trailer is moved by the loop carriage only when the rope length between the loop carriage and the respective trailer has been used up. When the rope drum is driven by a spring drum, there is the disadvantage that the springs have only a service life of a few months. If the rope drums are driven electrically, there is the disadvantage that each motor must have its own control and its own energy supply.
The horizontal strip storage unit for sheet metal strips according to Austrian patent 299,103, includes a movable loop carriage which is preferably drivable with a constant torque for increasing the length of the loop and a plurality of support carriages which are movable along guide rails. An endless rope guided around deflection rollers is connected to the loop carriage and the support carriages. The drive of the support carriages is provided by the rope through receiving rollers with the intermediate arrangement of reduction transmission units, so that there is an equal spacing between the support carriages when the loop carriage is moved. This strip storage unit has the particular disadvantage that a different transmission ratio is required for each carriage and that there is the danger that dirt accumulates on the drive pinion and the rack, so that the drive and transmission conditions are not exact.
The horizontal strip storage unit according to European application 0,110,864 also includes a movable loop carriage which is coupled with individual support carriages by means of flexible traction members which can be pulled out against a restoring force. The traction members have to be elastically expandable at least over a certain length. The traction members are, for example, rubber ropes or the like, and are guided around deflection rollers to form a loop. The purpose of this construction is to provide an impact-free drive of the support carriage by the loop carriage, while simultaneously ensuring a uniform distance between the individual support carriages. This strip storage unit has the disadvantage that the flexible or elastic rubber ropes age relatively quickly and become brittle and, therefore, can wear in an uncontrolled manner and at a different rate, and that rubber ropes can be damaged relatively quickly in the demanding rolling mill operation, so that there is also the danger that the rubber ropes will break.
It is, therefore, the primary object of the present invention to provide a strip storage unit in which the above-described disadvantages are avoided and in which the connections between the support carriages and the loop carriage are substantially more durable. When the loop carriage is moved in order to change the length of the loop, the distances between the support carriages are to remain equal, so that an optimum guidance of the strip on the support rollers of the support carriages is ensured. In addition, the movement of the support carriages is to be without impact.